The invention relates to a liquid-cooled composite piston for internal combustion engines, particularly diesel engines, which piston comprises a lower part that is preferably made of an aluminum piston alloy and is forced by screws against the upper part, which is preferably made of a ferrous material. The upper part has an external cooling passage and an annular flange having a tongue which protrudes into the external cooling passage The annular flange is clamped between an annular rib, which is concentrically arranged on the inside of the upper portion, and a surface which is formed on the lower portion and faces said rib. The annular rib constitutes the radially inner boundary of the cooling passage. The cooling passage is formed in the upper portion behind the top land and at least part of the ring-carrying portion and is open toward the interfacial plane between the upper and lower parts of the piston. The annular rib surrounds a centrally disposed internal cooling chamber, which communicates with the cooling passage through radially extending coolant bores The annular rib is formed with tapped bores for the screws, and the cooling passage and the cooling chamber communicate with the system in which the coolant is circulated.